The importance and significance of sleep and dreams have occupied and puzzled people for thousands of years. Let us begin by defining sleep.

Prolonged rest without reaction to stimuli

The state of sleep can be described as a prolonged rest during which the body is relaxed and when the perception of our surroundings is absent, or at least clearly limited. The sleeper’s reaction to external stimuli (sound, light, touch, etc.) is greatly reduced during sleep.

The reactions display considerable individual differences, however, as well as being dependent on how deeply the person is sleeping. Light stimuli, on the other hand, such as the weak sound of voices or a partner’s movements in bed, are often incorporated into the content of dreams. In the event of strong stimuli, there is a rapid transition from sleep to an awakened state. Research has shown that the brain also receives and processes stimuli during sleep, even though we are not aware of this ourselves.